FIG. 9(a) is a perspective view showing the appearance of a 3.5 inch magneto-optical disk cartridge C on its surface side, and FIG. 9(b) is a perspective view showing the appearance of the magneto-optical disk cartridge C on its rear-surface side.
As illustrated in FIGS. 9(a) and 9(b), a rotatable disk 2 is housed inside the cartridge case 1 of the magneto-optical disk cartridge C. Further, a shutter 3, which is free to slide laterally, is installed on the surface of the cartridge case 1. The shutter 3 is closed when the magneto-optical disk cartridge C has been removed from a disk driving device, not shown. Thus, it is possible to protect the disk 2 and its central driving section from dust and dirt, and also to protect them from damage.
Moreover, as illustrated in FIG. 9(b), a location hole 6 and an alignment hole 7 are provided in the rear-surface of the magneto-optical disk cartridge C. The location hole 6 has a perfectly round shape. Here, a positioning pin 4 (see FIG. 11), which is attached to a disk driving device 40 (see FIG. 11) that will be described later, is fitted to the location hole 6 so that the original position for the magneto-optical disk cartridge C is determined with respect to the disk driving device 40.
The alignment hole 7, on the other hand, is an elongated hole. A positioning pin 5 (see FIG. 11), which is attached to the disk driving device 40, is fitted to the alignment hole 7 so that the planar position of the magneto-optical disk cartridge C is determined with respect to the disk driving device 40. Moreover, reference surfaces 8a, 8b, 8c and 8d of the cartridge case 1 come into contact with respective receiving faces of the disk driving device 40 so that the position of the magneto-optical disk cartridge C is determined with respect to the rotation-axis direction of the disk driving device 40.
Here, the following structures are exemplified as a disk hub 30 that is attached to the disk 2. The disk hub 30 is fitted to a spindle 31 (see FIG. 11) for rotating the disk 2, and transmits the rotational driving force of the spindle 31 to the disk 2.
FIG. 10(a) shows one structural example of the disk hub 30 that is attached to a disk of 90 mm (3.5 inch). The main body 30a of the disk-use hub 30 is molded from polycarbonate resin. Further, a magnetic plate 32, made of a magnetic metal such as, for example, SUS (Stainless Steel)-430, is inserted into the hub's main body 30a during its molding process. Moreover, a center hole 34 is provided in the center of the magnetic plate 32 by a draw-bending process.
A flange 30b is integrally formed around the periphery of the hub's main body 30a. Here, an energy director 30c, which is used for ultrasonically joining the disk, is provided on one side face of the flange 30b in a protruding ring shape.
FIG. 10(b) shows another structural example of the disk hub 30 that is attached to a disk of 130 mm (5.25 inch). Here, the members that have the same functions as those used in the above-mentioned disk hub 30 attached to the disk of 90 mm are indicated by the same reference numbers.
The main body 30a of this disk hub 30 is molded from polycarbonate resin, and a magnetic plate 32 is inserted to the hub's main body 30a during its molding process. Further, a hole-formation member 30d, which is made of another type of resin having a lower friction resistance, is formed at the central portion of the magnetic plate 32 during its molding process so that the center hole 34 is provided. Here, an energy director 30c is integrally formed on the hub's main body 30a.
Referring to FIGS. 11(a) and 11(b), the following description will discuss processes during which the magneto-optical disk cartridge C is placed into the disk driving device 40.
When the magneto-optical disk cartridge C is inserted into the cartridge entrance (not shown) of the disk driving device 40 from its front portion (a portion at which the shutter 3 (see FIG. 9) is provided), the shutter 3 is first opened. Then, as the magneto-optical disk cartridge C is further inserted, the positioning pins 4 and 5 inside the disk driving device 40 are respectively fitted into the location hole 6 and the alignment hole 7 (both shown in FIG. 9) that are formed in the cartridge case 1.
Coinciding with this positioning operation, the disk hub 30, provided in the center of the disk 2 that has been housed in the magneto-optical disk cartridge C, is allowed to fit to the spindle 31 that is provided in the disk driving device 40 in the following manner.
As illustrated in FIG. 11(a), the magnetic plate 32, which is attached to the disk hub 30 of the disk 2 that is located in a disk-housing space inside the cartridge case 1, is attracted to a magnet 33 that is attached to the spindle 31, and then the center hole 34 of the disk hub 30 is inserted into the spindle 31. In this case, the disk 2, which is placed in the disk-housing space inside the cartridge case 1, is allowed to slide into the spindle 31, while the center hole 34 is being aligned by the tip of the spindle 31. Consequently, as illustrated in FIG. 11(b), the disk 2 comes into contact with a disk clamp 35 that is fitted into the spindle 31, thereby completing the inserting operation.
After completion of the inserting operation of the magneto-optical disk cartridge C, the spindle 31 and the disk clamp 35 fitted into the spindle 31 are allowed to rotate. Then, the rotational driving force of the spindle 31 is transmitted to the disk 2 that is being pressed against the disk clamp 35 by a magnetic force, and the disk 2 rotates at a predetermined speed.
Here, when the center hole 34 of the disk hub 30 slides into the spindle 31 to fit thereto while being aligned by the tip of the spindle 31, abrasion takes place between the tip of the spindle 31 and the open edge of the center hole 34. Further, when the magneto-optical disk cartridge C is drawn from the disk device, abrasion also takes place between the outer circumferential surface of the spindle 31 and the inner circumferential surface of the center hole 34.
Therefore, in the conventional disk hub 30 shown in FIG. 10(a), since the metal spindle 31 and the center hole 34 of the metal magnetic plate 32 contact each other, both of the members are subjected to abrasion every time the inserting or drawing operation is repeated. The resulting problem is that the alignment accuracy is lowered. Moreover, in the above-mentioned disk hub 30, dust is raised due to the abrasion, and the dust, scattered in the periphery, causes adverse effects on the optical system and mechanical system of the disk driving device 40.
In the conventional disk-use hub 30 shown in FIG. 10(b), on the other hand, the above-mentioned problem is alleviated, since the hub's main body 30a is molded from a resin material suitable for the joining to the disk 2, and since the center hole 34 is provided as the hole-formation member 30d that is made of another type of resin having a low-friction resistance. However, this disk hub 30 is expensive with a complicated structure, and the processing cost is also high since two types of resin materials are used.